A girl and her mother were discovered dead under a mattress in a home in Roselle, New Jersey (Picture: REX)

A 9-year-old girl and her mother were allegedly axed to death by her uncle and found underneath a mattress in their home.

The pair were found inside a residence on West 7th Avenue in Roselle, New Jersey, on Wednesday after the girl did not turn up at school, WABC reported.

Prosecutors provided little details as the double homicide investigation was underway, but Atasha Scott, a sister of the homeowner, identified the victims to NBC New York as his daughter and wife.

The girl’s uncle, who is the brother of the homeowner, was ordered to leave the home and killed his niece and sister-in-law using an ax in the garage, according to Scott. The homeowner returned from work on Wednesday and saw bloody sheets and an ax left between mattresses, and called police.

Investigators were at the residence on West 7th Avenue in the morning of Thursday (Picture: ZUMA Press)

Investigators found the girl and her mother under a mattress, CBS News reported. They gathered evidence on Thursday morning.

The girl, named Kelsey, would have turned 10 years old on Sunday, according to Scott. Her uncle allegedly drove off with the mother’s new BMW.

A law enforcement source told NBC New York that the BMW was located in Maryland and that the uncle was arrested and faces a vehicle theft charge.

Investigators gathering evidence from the home on Thursday morning (Picture: Shutterstock)

Family members had been asking for information on where the girl and her mother were on social media.

Neighbors were jarred when they saw cops removing bags of evidence from the house.

‘I’ve never seen anything, very quiet and nice neighborhood,’ Alicia Mendez told CBS News. ‘It’s kind of scary, something like that might be happening.’

A heavy police presence was at the residence and blocks around the scene were closed to pedestrian traffic (Picture: Shutterstock)

Another neighbor, John Bambino, told the news outlet: ‘We were surprised to hear and nobody knew what was going on until they saw the police presence.’

The Union County Prosecutor’s Office said there was no threat to the public.

Schools in Rosevelle were on lockdown briefly on Wednesday and had students sheltering in place. It was lifted by the afternoon.

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Cops found the girl and her mother dead under a mattress after she did not turn up at school.